1. Field of the Invention
The present invention is directed to an apparatus and method for polishing an optical fiber, in particular, an optical fiber terminated and polished in the field.
2. Background
In the area of optical telecommunication networks, fiber optic connectors are one of the primary ways to connect two or more optical fibers. There are several classes of optical fiber connectors including adhesive ferruled connectors, in which the fiber tip is held in a substantially fixed position relative to the tip of the ferrule by adhesively securing the fiber within the bore of the ferrule. Another class of connectors includes non-ferrule connectors, which rely on the buckling of a length of fiber to create contact pressure. Another class of connectors includes remote grip (ferruled) connectors, where the fiber is secured at some distance away from the terminal end or tip of the fiber.
When installing a remote grip connector in the field, one current practice uses a coplanar/flush polish. In remote grip connectors, as with other connector types, low optical losses and minimal reflections are achieved when the terminal ends of at least two optical fibers make secure physical contact. However, any differences in the coefficient of expansion between the fiber and the ferrule assembly may result in a non-contacting fiber tip when the temperature is raised, or lowered. The resulting gap can lead to significant reflection. A conventional remote grip connector is described in U.S. Pat. Nos. 5,408,558 and 7,775,726.
Another current practice involves a technician performing a field polish to create a fiber terminal end which protrudes beyond the ferrule tip. This method of polishing remote grip connectors produces a range of protrusions that provide a secure physical contact while avoiding excess force on the fiber tips. This method, when carefully followed, allows sufficient physical contact of the at least two fiber terminal end faces at temperatures for indoor applications (0° C. to 60° C.). However, the conventionally polished field-terminated remote grip connector may not be recommended for outdoor use, which has more stringent temperature requirements (−40° C. to 80° C.). Factors leading to unacceptable optical loss may result from the intrinsic variability of the field polishing process, craftsman error, over polishing (e.g. using too much force or too many strokes and coarse, clogged or contaminated abrasive) or substitution of a different type of abrasive.
The following references describe conventional devices for polishing optical fibers: US 2011/0275283 A1; US 2011/0312249 A1; U.S. Pat. Nos. 3,975,865; 4,178,722; 4,291,502; 4,979,334; 5,007,209; 5,185,966; 5,216,846; 5,349,784; 5,351,445; 6,790,131; 6,945,860; and 7,491,114.